Process for producing a fuel from lignocellulosic feedstock

ABSTRACT

The present invention relates to a method for producing a composition for use in land application. The method comprises: (a) obtaining a fermentation product by a production process comprising the steps of: (i) treating lignocellulosic feedstock to produce sugar; (ii) fermenting the sugar to produce a fermented mixture comprising the fermentation product; and (iii) recovering the fermentation product from the fermented mixture in one or more stages to produce a concentrated fermentation product and still bottoms; and 
     (b) recovering the still bottoms, the still bottoms comprising organic and inorganic components; and (c) providing the still bottoms for use in a land application. Also provided is a soil conditioning composition for use in land application. The soil conditioning composition contains still bottoms and optionally other components.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/376,975, filed on Aug. 6, 2014, which is a national stage applicationof PCT/CA2013/050164 having an international filing date of Mar. 5,2013, which claims benefit of U.S. Provisional Application No.61/634,758, filed Mar. 5, 2012. The entire contents of theaforementioned applications are incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a composition for use in landapplication and methods for producing same.

BACKGROUND OF THE INVENTION

Fuel ethanol is currently produced from feedstocks such as corn starch,sugar cane, and sugar beets. However, the production of ethanol fromlignocellulose-containing feedstocks, such as agricultural wastes andforestry wastes has received much attention in recent years. Anadvantage of using these feedstocks is that they are widely availableand can be obtained at low cost. Furthermore, a byproduct of theconversion process, known as lignin, can be used as a fuel to power theprocess instead of fossil fuels. Several studies have concluded that,when the entire production and consumption cycle is taken into account,the use of ethanol produced from cellulose generates close to nilgreenhouse gases.

The processing steps for converting lignocellulosic feedstock toethanol, or other fuels and chemicals, involve breaking down the fibrouslignocellulosic material by a series of chemical and biologicaltreatments to liberate sugar monomers from the feedstock. There arevarious known methods for producing fermentable sugars fromlignocellulosic feedstocks, one of which involves a chemicalpretreatment followed by hydrolysis of cellulose with cellulase enzymesand β-glucosidase. The sugars produced in hydrolysis are fermented to afermentation product in a fermentation carried out subsequent to, orduring the hydrolysis of cellulose, using a microorganism such as yeastor bacteria. The fermentation product produced from the lignocellulosicfeedstock may be concentrated by any suitable technique. For example, inthe production of ethanol, distillation is carried out subsequent tofermentation to recover the ethanol in concentrated form and residualwater is subsequently removed by molecular sieves or by othertechniques. The residue remaining after concentrating the fermentationproduct is referred to as “still bottoms” or a “still bottoms stream”.

Although there have been research efforts devoted to producing fuel orother chemicals from lignocellulosic feedstock, the existingtechnologies have been difficult to commercialize. At present, the costof producing fuels and other chemicals from lignocellulosic feedstock isstill relatively high.

One problem with processes for converting lignocellulosic feedstock to afuel or other chemical is that the handling and disposal of the stillbottoms presents challenges. Disposal of still bottoms is costly,complex and has negative environmental implications. A disposal methodthat has been proposed for still bottoms derived from cellulosicconversion processes is biological waste water treatment. Another knownwaste disposal option is incineration, which allows the recovery of heatfrom the combustion of organics. A further option available for disposalis landfilling the still bottoms. While technically feasible, many ofthese options for handling and/or disposing of still bottoms requiresignificant capital and operation expenditure. Furthermore, processingthe still bottoms to recover inorganic sulfate salts by ion exclusionand using the recovered salts as a fertilizer has also been disclosed,as set forth in U.S. Pat. No. 7,670,813. However, it would be desirableto provide improved or alternate methods for managing still bottomsstreams comprising salts arising from processes for producingfermentation products from lignocellulosic feedstocks.

SUMMARY OF THE INVENTION

The process of the present invention overcomes, ameloriates or providesuseful alternatives in relation to known processes for handling anddisposing of waste streams arising during the processing oflignocellulosic feedstocks to produce a fermentation product for use asa fuel or chemical.

According to a first aspect, the present invention provides a processfor obtaining a composition for use in soil conditioning or landapplication from a process that produces a fermentation product from alignocellulosic feedstock. The process comprises: (a) producing thefermentation product by a production process comprising: (i) treatingthe lignocellulosic feedstock to produce sugar; (ii) fermenting thesugar to produce a fermented mixture comprising the fermentationproduct; and (iii) recovering the fermentation product from thefermented mixture in one or more stages to produce a concentratedfermentation product and still bottoms. The still bottoms are recoveredand subsequently provided for use in a land application or soilconditioning.

Advantageously, the still bottoms comprise organic and inorganiccomponents, both of which can provide benefits to soils. The inorganiccomponents satisfy nutrients for plant growth, for example nitrogen,sulfur and potassium. In addition, the organic components of the stillbottoms improve soil condition by increasing the water holding capacity,improving soil health and/or reducing erosion of top soil. Resultspresented herein show that still bottoms arising from productionprocesses using lignocellulosic feedstocks provide similar nutrientuptake in crops as chemical fertilizer. Further, as described herein,test results show that the still bottoms are not toxic to the plants.Crops that were treated with still bottoms of the invention had asimilar number of plants/hectare as crops treated with chemicalfertilizer.

In addition to these benefits to crops, the method disclosed hereinprovides a simpler alternative to the disposal of waste that resultswhen producing a fermentation product from a lignocellulosic feedstock.In contrast to other methods proposed for disposal of still bottoms, thepresent invention offers reduced operating and capital costs. Forexample, incineration and waste water treatment of still bottomsrequires significant capital to implement and high operating costs forthe plant. Landfilling is also a costly alternative and has negativeenvironmental implications. Thus, the present invention provides a lowcost soil conditioning composition from a waste stream that wouldotherwise require significant capital and operating cost for disposal.

Furthermore, the present invention overcomes concerns arising fromremoving crop residue remaining on a field after a crop has beenharvested. In particular, there have been concerns that removing cropresidues to make fuels and chemicals removes water, carbon, andnutrients from the soil. On the other hand, it is often desirable toremove crop residue build-up, especially from high yield crops, asexcessive residue can be difficult and expensive to manage.Advantageously, the present invention addresses concerns regarding cropresidue management, while also providing a cost-effective means forreturning organic matter and nutrients back to the soil.

In addition, by carrying out the present invention, life cyclegreenhouse gas emissions associated with production of a fuel from alignocellulosic feedstock are reduced relative to fuel productionprocesses that dispose of the still bottoms by other techniques, such asincineration or landfilling. The greenhouse gas reductions are achievedbecause of reduced dependence on chemical fertilizer. As chemicalfertilizer is synthesized using fossil fuels such as natural gas andcoal, by using nutrients from the still bottoms rather than chemicalfertilizer, greenhouse gas emissions savings can be achieved.Furthermore, unlike incineration, the invention does not require the useof scrubbing chemicals, which can also contribute to the life cyclegreenhouse gas emissions of the fuel.

According to certain embodiments of the first aspect of the invention,the inorganic components of the still bottoms originate from thelignocellulosic feedstock, process chemicals added during the productionprocess, or a combination thereof. In another embodiment, the inorganiccomponents originate from both the lignocellulosic feedstock and processchemicals added during the production process.

According to a further embodiment of the first aspect of the invention,the step of treating the lignocellulosic feedstock to produce sugarcomprises pretreating the lignocellulosic feedstock with acid or alkalito produce a composition comprising cellulose and hydrolyzing at least aportion of the cellulose to glucose with enzymes.

In a second aspect of the invention, the inorganic component of thestill bottoms comprises inorganic salt that comprises asulfur-containing salt. According to this aspect of the invention, thesulfur-containing salt originates in large part from sulfur-containingprocess chemicals added during the production process. The inventorshave recognized that still bottoms comprising sulfur-containing saltsoriginating from the process itself are particularly suitable for use inland application, such as for use as a fertilizer. The sulfur serves asa nutrient for plants, while the organic component provides organicmatter for the soil. In addition, this aspect of the invention providesa cost effective methodology for using a waste stream comprisingbyproducts arising from chemical addition steps that otherwise requirecomplex processes to treat and dispose of. For example, streamscontaining sulfate salts produce ash in boilers during incineration andare difficult to treat by anaerobic digestion as the salts can reducethe performance of the microorganisms. Not only do certain processesdisclosed herein overcome these limitations by reducing or eliminatingthe need for costly treatment methods, but the sulfur-containing saltscontained within the stream add nutrient value to the still bottoms whenused in land application.

Thus, according to a second aspect of the invention, there is provided aprocess for obtaining a composition for use in land applicationcomprising: (a) obtaining a fermentation product by a production processcomprising the steps of: (i) treating a lignocellulosic feedstock toproduce sugar; (ii) fermenting the sugar to produce a fermented mixturecomprising the fermentation product; and (iii) recovering thefermentation product from the fermented mixture in one or more stages toproduce a concentrated fermentation product and still bottoms; (b)recovering the still bottoms, the still bottoms comprising an organicand an inorganic component; and (c) providing the still bottomscomprising the organic component and inorganic component for use in aland application, wherein the inorganic component of the still bottomscomprises inorganic salt that arises from one or more sulfur-containingprocess chemicals that are used during the production process andwherein the inorganic salt is a sulfur-containing salt. According to anembodiment of this aspect of the invention, the one or moresulfur-containing process chemicals that are used during the productionprocess include sulfuric acid. According to another embodiment of thisaspect of the invention, the one or more sulfur-containing processchemicals are used during the step of treating the lignocellulosicfeedstock to produce sugar. The sulfur-containing salt may be a sulfatesalt selected from ammonium sulfate and calcium sulfate. In a preferredembodiment, the sulfate salt is ammonium sulfate.

According to any of the foregoing aspects of the invention, the step oftreating the lignocellulosic feedstock to produce sugar may comprise(i′) pretreating the lignocellulosic feedstock with sulfuric acid toproduce an acid pretreated lignocellulosic feedstock and adding alkalito the acid pretreated lignocellulosic feedstock to adjust the pHbetween about 4 and about 7, thereby producing a sulfur-containing salt;or (ii′) pretreating the lignocellulosic feedstock with alkali toproduce an alkali pretreated lignocellulosic feedstock and addingsulfuric acid to the alkali pretreated lignocellulosic feedstock toadjust the pH between about 4 and about 7, thereby producing asulfur-containing salt, wherein the sulfur-containing salt produced instep (i′) or (ii′) forms at least part of the inorganic component of thestill bottoms.

After the pH adjustment, the pretreated feedstock may be hydrolyzed withan enzyme mixture comprising at least cellulase enzymes. According tocertain embodiments of any of the aforesaid aspects of the invention, atleast part of the steps of treating to produce sugar and fermenting arecarried out as part of a simultaneous saccharification and fermentationprocess.

The acid pretreated feedstock is preferably adjusted with alkaliselected from lime, ammonia and ammonium hydroxide. This producesinorganic salt selected from calcium sulfate and ammonium sulfate. In anembodiment, the acid pretreated feedstock is adjusted with ammonia orammonium hydroxide, which produces ammonium sulfate. The ammoniumsulfate then forms at least part of the inorganic component of the stillbottoms. In another embodiment of the invention, the acid pretreatedfeedstock is adjusted with lime, which produces calcium sulfate.

In yet further embodiments of the invention, in the step of treating thelignocellulosic feedstock to produce sugar, alkali selected from lime,ammonia and ammonium hydroxide is used to pretreat the feedstock toproduce alkali pretreated feedstock. When alkali selected from lime,ammonia and ammonium hydroxide are used to pretreat the feedstock, thepH adjustment with sulfuric acid produces inorganic salt selected fromammonium sulfate and calcium sulfate. The ammonium sulfate or calciumsulfate then forms at least part of the inorganic component of the stillbottoms. In an embodiment of the invention, the alkali used to pretreatthe feedstock is ammonia or ammonium hydroxide, and the alkalipretreated feedstock is adjusted with sulfuric acid which producesammonium sulfate. The ammonium sulfate then forms at least part of theinorganic component of the still bottoms. Ammonium sulfate providesnitrogen and sulfur in the still bottoms, both of which can increase thenutrient content of soil.

According to an embodiment of any of the foregoing aspects of theinvention, the still bottoms has a sulfur content of between about 1.0and about 15 wt %, between about 1.0 and about 12 wt %, between about1.5 and about 12 wt % or between about 2.0 and about 8 wt % as measuredon a dry basis. In yet further embodiments, the still bottoms has asulfur content of between about 0.5 and about 15 wt %, between about 0.5and about 12 wt % or between about 0.5 and about 8 wt %. The sulfurcontent may include ranges having numerical limits of about 0.5, 1.0,1.5, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10, 11, 12, 13, 14 or 15 wt% as measured on a dry basis.

According to an embodiment of any of the foregoing aspects of theinvention, the still bottoms has a nitrogen content of between about 2.0and about 12 wt %, between about 2.0 and about 10 wt %, or between about2.0 and about 8 wt % on a dry basis. In further embodiments, the soilconditioning composition has a nitrogen content of between about 1.0 andabout 15 wt %, between about 1.0 and about 12 wt %, between about 1.0and about 10 wt % or between about 1.0 and about 8 wt % on a dry basis.The nitrogen content may include ranges having numerical limits of about0.5, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10, 11, 12, 13,14 or 15 wt % as measured on a dry basis.

In another embodiment of the invention, the still bottoms has aphosphorus content of less than 2 wt % as measured on a dry basis.

In certain embodiments of the invention, the still bottoms provided foruse in the land application comprises about 40-80 wt % organiccomponents and about 20-60 wt % inorganic components measured on a drybasis. The organic component may comprise dissolved lignin, insolublelignin or a combination thereof.

In a further embodiment of any of the foregoing aspects of theinvention, the still bottoms has a solids content that allows it to beland applied through conventional farming equipment.

The step of recovering in any of the foregoing aspects of the inventionmay comprise concentrating the still bottoms. In a further embodiment,the step of recovering comprises separating solids from the stillbottoms, thereby producing a residue stream composed of separated solidsand a liquid component and wherein the separated solids and the liquidcomponent are each provided for use in soil conditioning.

In an embodiment of either of the foregoing aspects of the invention,the still bottoms are directly applied to land or concentrated and thenapplied directly to land, without any intervening waste water treatment,including biological or chemical treatment.

According to a further aspect, the present invention provides a methodfor using still bottoms as a fertilizer or soil conditioning compositioncomprising applying to land still bottoms produced by a productionprocess that utilizes a lignocellulosic feedstock to produce afermentation product.

According to certain embodiments of this aspect of the invention, thesoil conditioning composition comprises about 40-80 wt % organiccomponents and about 20-60 wt % inorganic components, on a dry basis.The inorganic components may originate from the lignocellulosicfeedstock, process chemicals added during the production process, or acombination thereof. Preferably, the inorganic components originate fromboth the lignocellulosic feedstock and process chemicals added duringthe production process. The organic components may comprise dissolvedlignin, insoluble lignin, or a combination thereof. Other organiccomponents include residual carbohydrates, non-fermented sugars,polyols, fermentation solids or a combination thereof. According to oneembodiment, there is no insoluble lignin.

According to further embodiments, the still bottoms component of theconditioning composition has a phosphorus content of less than about 2wt % measured on a dry basis.

The method of the invention may further comprise mixing the soilconditioning composition with manure prior to the step of applying it toland.

According to another aspect, the invention provides a soil conditioningcomposition comprising: still bottoms comprising: about 40-80 wt %organic component; and about 20-60 wt % inorganic component, wherein theorganic component comprises soluble lignin and the inorganic componentcomprises nitrogen and sulfur.

The water content of the soil conditioning composition may be betweenabout 10 and about 90 wt %, or between about 20 and about 50 wt %. Infurther embodiments, the soil conditioning composition is composed ofseparated still bottoms solids resulting from a step of separatingsolids from a still bottoms stream.

The organic component of the soil conditioning composition may compriseresidual carbohydrates, non-fermented sugars, polyols, fermentationsolids, dissolved lignin, or a combination thereof. The organiccomponent of the soil conditioning composition may further compriseinsoluble lignin. In further embodiments of the invention, the soilconditioning composition further comprises potassium, chloride,magnesium, calcium, or a combination thereof. In yet furtherembodiments, the still bottoms in the soil conditioning composition hasa phosphorus content of less than 2 wt % on a dry basis.

According to an embodiment of the invention, the soil conditioningcomposition has a sulfur content of between about 1.0 and about 15 wt %,between about 1.0 and about 12 wt %, between about 1.5 and about 12 wt %or between about 2.0 and about 8 wt % as measured on a dry basis. In yetfurther embodiments, the still bottoms has a sulfur content of betweenabout 0.5 and about 15 wt %, between about 0.5 and about 12 wt % orbetween about 0.5 and about 8 wt %. The sulfur content may includeranges having numerical limits of about 0.5, 1.0, 1.5, 2.0, 3.0, 4.0,5.0, 6.0, 7.0, 8.0, 9.0, 10, 11, 12, 13, 14 or 15 wt % as measured on adry basis.

According to an embodiment of the invention, the soil conditioningcomposition has a nitrogen content of between about 2.0 and about 12 wt%, between about 2.0 and about 10 wt %, or between about 2.0 and about 8wt % on a dry basis. In further embodiments, the soil conditioningcomposition has a nitrogen content of between about 1.0 and about 15 wt%, between about 1.0 and about 12 wt %, between about 1.0 and about 10wt % or between about 1.0 and about 8 wt % on a dry basis. The nitrogencontent may include ranges having numerical limits of about 0.5, 1.0,1.5, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10, 11, 12, 13, 14 or 15 wt% as measured on a dry basis.

According to a further embodiment of the invention, the inorganiccomponent of the soil conditioning composition comprises a sulfate salt.In another embodiment of the invention, the inorganic componentcomprises ammonium sulfate or calcium sulfate. In yet a furtherembodiment, the inorganic component comprises ammonium sulfate.

In a further aspect, the present invention provides a soil conditioningcomposition for use in land application that comprises still bottoms,wherein the still bottoms are derived from a method that produces afermentation product from a lignocellulosic feedstock.

According to another aspect of the invention there is provided a methodcomprising (i) obtaining a soil conditioning composition that comprisesstill bottoms, wherein the still bottoms are derived from a method thatproduces a fermentation product from a lignocellulosic feedstock; and(ii) adding insoluble lignin to the soil conditioning composition ofstep (i) prior to its use in land application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a bar graph showing the nitrogen (N), phosphorus (P),potassium (K), sulfur (S), lignin and moisture content of a soilconditioning composition comprising still bottoms. The nitrogen,phosphorus, potassium, sulfur, lignin and moisture content of the stillbottoms are measured on a wet (first bars) or dry basis (second bars).

FIG. 2A is a bar graph showing the leaf tissue sulfur (S) content (%) ofcorn samples after application of still bottoms (first bars) andchemical fertilizer (second bars) to corn crops at nitrogen rates of 50,100, 150 and 200 lbs/acre. Results are also shown with no fertilizer(labeled no nitrogen).

FIG. 2B is a bar graph showing the leaf tissue phosphorus (P) content(%) of corn samples after application of still bottoms (first bars) andchemical fertilizer (second bars) to corn crops at nitrogen rates of 50,100, 150 and 200 lbs/acre. Results are also shown with no fertilizer(labeled no nitrogen).

FIG. 2C is a bar graph showing the leaf tissue potassium (K) content (%)of corn samples after application of still bottoms (first bars) andchemical fertilizer (second bars) to corn crops at nitrogen rates of 50,100, 150 and 200 lbs/acre. Results are also shown with no fertilizer(labeled no nitrogen).

FIG. 2D is a bar graph showing the leaf tissue nitrogen (N) content (%)of corn samples after application of still bottoms (first bar) andchemical fertilizer (second bar) to corn crops at nitrogen rates of 50,100, 150 and 200 lbs/acre. Results are also shown with no fertilizer(labeled no nitrogen).

FIG. 3 is a bar graph showing the chlorophyll content at the tasselingstage of corn after application of still bottoms (first bars) andchemical fertilizer (second bars) to corn crops at nitrogen rates of 50,100, 150 and 200 lbs/acre. Results are also shown with no fertilizer(labeled no nitrogen).

FIG. 4 is a bar graph showing corn plants/hectare after application ofstill bottoms (first bars) and chemical fertilizer (second bars) to corncrops at nitrogen rates of 50, 100, 150 and 200 lbs/acre. Results arealso shown with no fertilizer (labeled no nitrogen).

DETAILED DESCRIPTION OF THE INVENTION

The following description is of a preferred embodiment by way of exampleonly and without limitation to the combination of features necessary forcarrying the invention into effect. The headings provided are not meantto be limiting of the various embodiments of the invention. Terms suchas “comprises”, “comprising”, “comprise”, “includes”, “including” and“include” are not meant to be limiting.

The process of the present invention comprises producing sugar from alignocellulosic feedstock and fermenting the sugar to produce afermentation product in the same or different stages. The fermentationproduct includes any product or byproduct of the fermentation for use asa fuel, fuel intermediate or chemical. In one embodiment of theinvention, the fermentation product is an alcohol.

Description of Feedstock Types

By the term “lignocellulosic feedstock”, it is meant any type of woodyor non-woody plant biomass, or feedstock derived from plant biomass,such as, but not limited to,

-   -   (i) biomass crops such as, dedicated biomass crops, including,        but not limited to, grasses, for example, C4 grasses, such as        switch grass, cord grass, rye grass, miscanthus, reed canary        grass, or a combination thereof;    -   (ii) residues, byproducts or waste from the processing of plant        biomass, or feedstock derived from plant biomass, in a facility        to yield food or non-food products, for example, but not limited        to, residues remaining after obtaining sugar from plant biomass        such as sugar cane bagasse, beet pulp, or residues remaining        after removing sugar from Jerusalem artichoke, or a combination        thereof; and residues remaining after grain processing, such as        corn fiber, corn stover, or a combination thereof;    -   (iii) agricultural residues, for example, but not limited to,        soybean stover, corn stover, rice straw, sugar cane straw, rice        hulls, barley straw, corn cobs, wheat straw, canola straw, oat        straw, oat hulls, corn fiber, or a combination thereof;    -   (iv) forestry biomass for example, but not limited to, recycled        wood pulp fiber, sawdust, hardwood, for example aspen wood,        softwood, or a combination thereof;    -   (v) waste material derived from pulp and paper products such as        newsprint, cardboard, or a combination thereof and    -   (vi) municipal waste.

Lignocellulosic feedstock may comprise one species of fiber or,alternatively, lignocellulosic feedstock may comprise a mixture offibers that originate from different lignocellulosic feedstocks. Inaddition, the lignocellulosic feedstock may comprise freshlignocellulosic feedstock, partially dried lignocellulosic feedstock,fully dried lignocellulosic feedstock, or a combination thereof.Moreover, new lignocellulosic feedstock varieties may be produced fromany of those listed above by plant breeding or by genetic engineering.

Lignocellulosic feedstocks comprise cellulose in an amount greater thanabout 20%, more preferably greater than about 30%, more preferablygreater than about 40% (w/w). For example, the lignocellulosic materialmay comprise from about 20% to about 50% (w/w) cellulose, or any amounttherebetween. Furthermore, the lignocellulosic feedstock compriseslignin in an amount greater than about 10%, more typically in an amountgreater than about 15% (w/w). Preferably, the lignocellulosic feedstockcomprises about 25% to about 45% (w/w) cellulose, about 15% to about 35%(w/w) xylan and about 10% to about 25% (w/w) lignin. The lignocellulosicfeedstock may also comprise sucrose, fructose and starch. Without beinglimiting, the amount of sucrose, fructose or starch present inlignocellulosic feedstocks is generally less than cellulose and xylan.

The lignocellulosic feedstock may be first subjected to size reductionby methods including, but not limited to, milling, grinding, agitation,shredding, compression/expansion, or other types of mechanical action.The lignocellulosic feedstock from the size reduction process mayproduce a size-reduced feedstock comprising particles of a definedlength. For example, at least 90% by weight of the particles in the sizereduced feedstock may have a length less than between about ⅛ and about8 inches. As would be appreciated by those of ordinary skill in the art,lignocellulosic feedstock that has been subjected to size reductioncomprises feedstock particles having a range of sizes and shapes.

The feedstock is optionally slurried. Slurrying of the feedstock allowsit to be pumped readily and may be carried out in any suitable batch orcontinuous mixing vessel, including a standpipe or pulper. Slurrying maybe distinct from the water and chemical addition or may occursimultaneously therewith.

Slurrying can occur at any suitable consistency selected by those ofordinary skill in the art. However, in practice, the consistency of theincoming feedstock slurry utilized will depend on the specific mixingmeans employed and the specific pumps used. In one embodiment of theinvention, the consistency of the feedstock slurry is between about 2%and about 40% (w/w) or more typically between about 4% and about 30%(w/w).

Treatment of the Lignocellulosic Feedstock to Produce Sugar

Any of a variety of methods may be employed for treating lignocellulosicfeedstock to produce sugar, including treating the lignocellulosicfeedstock using mechanical, chemical, thermal and/or biologicaltreatments. Fermentable sugar may be obtained from lignocellulosicfeedstock using techniques that are known to those of ordinary skill inthe art, or later-developed techniques, including, but not limited tothose described below. Treating the lignocellulosic feedstock to producesugar may be a single treatment or more preferably is carried out inmultiple stages.

The lignocellulosic feedstock may be pretreated by reacting it underconditions that disrupt the fiber structure and that increase thesusceptibility or accessibility of cellulose within the cellulosicfibers for subsequent conversion steps, such as enzymatic hydrolysis. Inone embodiment of the invention, the pretreatment is performed so that ahigh degree of hydrolysis of the hemicellulose and only a small amountof conversion of cellulose to glucose occurs. Pretreatment may beconducted in one or multiple stages. The cellulose may be hydrolysed toglucose in a subsequent step that uses cellulase enzymes.

For acid pretreatment, the pH is typically between about 0.4 and about3.5. Acid pretreatment is preferably carried out at a maximumtemperature of about 160° C. to about 280° C. The time that thefeedstock is held at this temperature may be about 6 seconds to about3600 seconds. The pretreatment is typically carried out under pressure.For example, the pressure during pretreatment may be between about 350and about 6500 kPa, or any pressure range therebetween. The feedstockmay be heated with steam during or prior to pretreatment.

The acid pretreatment produces a composition comprising an acidpretreated feedstock. Sugars produced by the hydrolysis of hemicelluloseduring acid pretreatment include xylose, glucose, arabinose, mannose,galactose or a combination thereof.

Pretreatment may also be carried out under alkaline conditions. Examplesof suitable alkaline pretreatment processes include ammonia fiberexpansion (AFEX) or dilute ammonia pretreatment. Other pretreatmentmethods include mechanical and hydrothermal pretreatment andpretreatment with organic solvents (known in the industry as Organosolv™pretreatment).

According to one exemplary embodiment of the invention, the solublecomponents of the pretreated feedstock composition are separated fromthe solids. The aqueous stream, which includes the sugars releasedduring pretreatment, the pretreatment chemical and other solublecomponents, may then be fermented using a microorganism capable offermenting the sugars derived from the hemicellulose component of thefeedstock.

Subsequent to pretreatment, the pretreated feedstock slurry is typicallycooled to decrease its temperature to a range at which the cellulaseenzymes are active. It should be appreciated that cooling of thefeedstock can occur in a number of stages utilizing flashing, heatexchange or other suitable means.

Enzymatic Hydrolysis

The hydrolysis of the cellulose to soluble sugars can be carried outwith any type of cellulase enzymes suitable for such purpose andeffective at the pH and other conditions utilized, regardless of theirsource. Among the most widely studied, characterized and commerciallyproduced cellulases are those obtained from fungi of the generaAspergillus, Humicola, Chrysosporium, Melanocarpus, Myceliophthora,Sporotrichum and Trichoderma, and from the bacteria of the generaBacillus and Thermobifida. The conversion of cellobiose to glucose iscarried out by the enzyme β-glucosidase. By the term “β-glucosidase”, itis meant any enzyme that hydrolyses the glucose dimer, cellobiose, toglucose.

In addition, there are several accessory enzymes that aid in theenzymatic digestion of cellulose (see co-owned WO 2009/026722 (Scott),which is incorporated herein by reference, and Harris et al., 2010,Biochemistry, 49:3305-3316). These include EGIV, also known as Cel61,swollenin, expansin, lucinen and cellulose-induced protein (Cip).Glucose can be enzymatically converted to the dimers gentiobiose,sophorose, laminaribiose and others by beta-glucosidase viatransglycosylation reactions.

An appropriate cellulase dosage can be about 1.0 to about 40.0 FilterPaper Units (FPU or IU) per gram of cellulose, or any amounttherebetween. The FPU is a standard measurement familiar to thoseskilled in the art and is defined and measured according to Ghose (Pureand Appl. Chem., 1987, 59:257-268; which is incorporated herein byreference). A preferred cellulase dosage is about 10 to 20 FPU per gramcellulose.

The enzymatic hydrolysis can be conducted at a pH between about 4.0 and7.0. If acid pretreatment is utilized, the pH of the feedstock will beincreased with alkali to about pH 4.0 to about 7.0 prior to enzymatichydrolysis, or more typically between about 4.0 and about 6.0. Theoptimal pH range of most cellulases is between pH 4.0 and 6.0. However,cellulases with pH optima at more acidic and more alkaline pH valuescould be used. As discussed below, the addition of alkali at this stageof the process produces salts that can be recovered for use as afertilizer, depending on the identity of the alkali used in the process.

The temperature of the slurry is adjusted so that it is within theoptimum range for the activity of the cellulase enzymes. Generally, atemperature of about 45° C. to about 70° C., or about 45° C. to about65° C., or any temperature therebetween, is suitable for most cellulaseenzymes. However, the temperature of the slurry may be higher forthermophilic cellulase enzymes.

The hydrolysis may be conducted simultaneously with fermentation in asimultaneous saccharification and fermentation, also referred to as“SSF”. SSF is typically carried out at temperatures of 35 to 38° C.,which is a compromise between the 50° C. optimum for cellulase and the28° C. optimum for yeast.

The stream resulting from hydrolysis may comprise process chemicals,salts, proteins, and other organics derived from the feedstock, and aninsoluble solids phase, comprised of lignin, unreacted polysaccharide,and other water insoluble components. Lignin may be separated from thehydrolysate at this stage of the process or may be carried through tofermentation.

Fermentation

Fermentation of the sugar is carried out to produce the fermentationproduct.

The fermentative production of alcohol may be carried out with yeast orbacteria. A yeast that may be used for ethanol production is aSaccharomyces spp. yeast. Glucose and any other hexoses present in thesugar stream may be fermented to ethanol by wild-type Saccharomycescerevisiae, although genetically modified yeasts may be employed aswell.

The fermentation is typically conducted at a pH between about 4.0 andabout 6.0, or between about 4.5 and about 6.0. To attain the foregoingpH range for fermentation, it may be necessary to add alkali to thefermentation sugar feed stream. The fermentation sugar feed stream willcomprise one or more sugar monomers derived from cellulose,hemicellulose or both polymeric components. Sugar monomers derived fromcellulose include glucose, while hydrolysis of the hemicellulosecomponent yields such sugars as xylose, glucose, arabinose, mannose,galactose, or a combination thereof.

Xylose and arabinose that are derived from the hemicellulose may also befermented to a fermentation product by a yeast strain that naturallycontains, or has been engineered to contain, the ability to fermentthese sugars to ethanol. Examples of microbes that have been geneticallymodified to ferment xylose include recombinant Saccharomyces strainsinto which has been inserted either (a) the xylose reductase (XR) andxylitol dehydrogenase (XDH) genes from Pichia stipitis (U.S. Pat. Nos.5,789,210, 5,866,382, 6,582,944 and U.S. Pat. No. 7,527,927 and EuropeanPatent No. 450,530) or (b) fungal or bacterial xylose isomerase (XI)gene (U.S. Pat. Nos. 6,475,768 and 7,622,284). Examples of yeasts thathave been genetically modified to ferment L-arabinose include, but arenot limited to, recombinant Saccharomyces strains into which genes fromeither fungal (U.S. Pat. No. 7,527,951) or bacterial (WO 2008/041840)arabinose metabolic pathways have been inserted.

A typical temperature range for the fermentation of glucose to ethanolusing Saccharomyces cerevisiae is between about 25° C. and about 38° C.,although the temperature may be higher if the yeast is naturally orgenetically modified to be thermostable. The dose of the fermentationmicroorganism will depend on factors, such as the activity of thefermentation microorganism, the desired fermentation time, the volume ofthe reactor and other parameters. These parameters may be adjusted asdesired to achieve optimal fermentation conditions.

The fermentation may also be supplemented with additional nutrientsrequired for the growth of the fermentation microorganism. For example,yeast extract, specific amino acids, phosphate, nitrogen sources, salts,trace elements and vitamins may be added to the fermentation sugar feedstream to support their growth.

Fermentation of the sugar produces a fermented mixture comprising thefermentation product. The fermented mixture comprises organic andinorganic components, including any components added during thefermentation to support growth of the microorganisms.

Recovery of the Fermentation Product

By recovering the fermentation product from the fermented mixture, it ismeant removing the fermentation product from the fermented mixture tomake the fermentation product more concentrated and purer in one or morestages.

In an embodiment of the invention, the fermentation product is analcohol. A conventional technique for recovering alcohol in moreconcentrated and purer form is distillation. As used herein, the term“distillation” also encompasses steam and vacuum stripping. Othertechniques include membrane dehydration, pervaporation carried outdirectly on the fermented mixture or to replace concentration stepsafter distillation (such as molecular sieves).

The fermentation beer that is sent to distillation is a dilute alcoholsolution. Microorganisms are potentially present depending upon whetheror not they are removed from the beer by filtration or other means priordistillation of the beer. The beer may additionally contain anycomponents added during the fermentation to support growth of themicroorganisms. The beer will also contain any organics that have notbeen consumed by the microorganisms, along with soluble and insolubleinorganic salts.

The beer is pumped through one or more distillation columns to separatethe alcohol from the other components in the beer. The column(s) in thedistillation unit is preferably operated in a continuous mode, althoughit should be understood that batch processes are also encompassed by thepresent invention. Furthermore, the column(s) may be operated at anydesired pressure or vacuum. Heat for the distillation process may beadded at one or more points either by direct steam injection orindirectly via heat exchangers. The distillation unit may contain one ormore separate beer and rectifying columns, or a distillation column maybe employed that comprises an integral enriching or rectificationsection. The alcohol vapour is further purified to fuel grade ethanolspecification by removing residual water vapour by any of severalwell-known techniques.

The ethanol vapor is further purified to fuel grade specification byremoving residual water or water vapor by any of several well-known orlater-developed techniques.

When the alcohol has a higher boiling point than water, such as butanol,the distillation is run to remove the water and other volatile compoundsfrom the alcohol. The water vapor exits the top of the distillationcolumn and is known as the “overhead stream”.

Lignin Separation

The insoluble lignin may be recovered during the production process orit may be carried through to the still bottoms. If insoluble lignin isrecovered, it may be obtained from any stage of the production process.This is typically after the pretreatment, although processes are knownin which lignin is recovered in earlier stages of the productionprocess. Without being limiting, streams from which the lignin can beseparated include the hydrolysate stream comprising glucose resultingfrom enzymatic hydrolysis, the fermentation beer stream or the stillbottoms stream remaining after distillation. It should be understoodthat unconverted cellulose and other insoluble components may be carriedforward with the lignin during the lignin separation.

The lignin may be separated using conventional solid-liquid separationtechniques prior to any further processing. Such separation techniquesmay include the use of pressure or vacuum filters, centrifugal filtersor centrifuges, membrane filtration systems or gravity settlers. Thesolids content of the lignin stream resulting from the separation istypically greater than about 30 wt %, more typically greater than about50 wt %. The lignin may or may not be washed to recover additionalsugars and to remove process chemicals. Without being limiting, aparticularly suitable device for lignin separation is a filter press.

Still Bottoms Recovery

Recovery of the still bottoms involves obtaining the still bottomsremaining after concentration of the fermentation product, such as fromthe bottom of a distillation column or beer column. Without beinglimiting, the recovery may encompass processing steps prior to providingthe still bottoms for use in soil conditioning or land application.However, after processing, inorganic and organic components remain.Non-limiting examples of processing steps that may be carried out on thestill bottoms includes concentration, including solid/liquid separationtechniques, to produce still bottoms enriched in solids. Moreover,solids in the still bottoms may settle, for example during storage, andthese solids may be recovered and used for soil conditioning or landapplication. Optionally, a liquid component obtained from the stillbottoms is also provided for use in soil conditioning or landapplication, along with the still bottoms solids or as a separateproduct for land application.

According to the present invention, there is no or limited recovery ofinorganic salt from the still bottoms. As mentioned, inorganic saltsprovide nutrients for plant growth and/or improve soil condition. Thestill bottoms provided for use in a land application will generallycomprise at least about 50 wt %, or at least about 75 wt %, or morepreferably at least about 80 wt % of the inorganic salts present in theoriginal stream fed to the step of recovering the still bottoms.Furthermore, other components can be recovered from the still bottomsprior to its use in a land application, such as organic acids, includingacetic acid.

According to certain embodiments of the invention, the still bottoms arenot subjected to any waste water treatment, such as biological treatmentprior to its use in a land application. By biological treatment it ismeant that biocatalysts such as microorganisms or enzymes are not addedto the still bottoms prior to land application. For example, in oneexample of the invention, the still bottoms is not treated by anaerobicdigestion or aerobic digestion prior to its use in a land application.In a further example of the invention, the still bottoms are not treatedby anaerobic digestion prior to its use in a land application.

According to certain embodiments of the invention, the still bottoms arenot subjected to chemical treatment. By this it is meant that processchemicals are not added to the still bottoms, such as acids, bases,oxidants or flocculents.

Non-limiting examples of methods for concentration of the still bottomsthat may be carried out include evaporation, centrifugation, membraneseparation, settling or other suitable techniques. In some embodimentsof the invention, between about 10% and about 90% (w/w), or betweenabout 30% and about 90% (w/w) of the liquid is removed from the stillbottoms prior to its recovery for use in a land application.

In one embodiment of the invention, concentration of the still bottomsis carried out in an evaporator unit. The evaporation may be carried outin a single-stage evaporator or may be part of a multiple-effect system.Those of skill in the art can readily choose a suitable operatingtemperature for the evaporator unit. In embodiments of the invention,the operating temperature of the evaporator unit can be between about40° C. and about 145° C. It will be understood that the temperature ismeasured at the operating pressure, which is typically under vacuum orat atmospheric pressure, but can be at higher pressure.

The still bottoms can be stored prior to being supplied for use in landapplication. Storage is carried out in any suitable containment means,such as tanks, basins or lagoons. The still bottoms can be agitated orthere may be no agitation during storage. Ventilation and/or odourcontrol methods may be utilized if required.

As would be appreciated by those of skill in the art, storagerequirements would typically be based on agricultural growing seasonsand the location of the production facility. For instance, whensupplying the soil conditioning composition in the spring or fall,storage would generally occur during the winter. Storage requirementsmay also depend on the geographic location of the production facility asthis will have an impact on the growing season.

Soil Conditioning Composition

The present invention also provides a soil conditioning composition,which is a composition applied to the land with the objective ofimproving soil condition, nutrient levels in plant tissue, plant growthor a combination thereof, relative to no fertilizer application.Improvements in soil condition include increasing nutrients in the landand increasing organic content. The soil conditioning composition may becomposed solely of still bottoms, although other components may be addedas well including manure, or other components set forth below.

The soil conditioning composition comprises an organic component and aninorganic component originating from the still bottoms. According tocertain embodiments, the soil conditioning composition comprises: stillbottoms comprising: about 40-80 wt % organic components; and about 20-60wt % inorganic components on a dry basis. For example, the soilconditioning composition may comprise about 40, 45, 50, 55, 60, 65, 70,75, 80 wt % organic components and 20, 25, 30, 35, 40, 45, 50, 55 and 60wt % inorganic components on a dry basis. The compositional analysis ofthe still bottoms, including determination of the content of organiccomponents, inorganic components, sulfur, nitrogen, phosphorus or othercomponents described herein is carried out after concentrating the stillbottoms, such as, but not limited to evaporation, if such a step iscarried out. If the still bottoms is not concentrated, then thecompositional analysis is just after distillation. Furthermore, suchcompositional analysis will be carried out on the still bottoms itselfif no additional components are present in the soil conditioncomposition. If additional components besides still bottoms are present,the analysis is conducted after the addition or such components. Thenitrogen (N), phosphorus (P), potassium (K) and sulfur (S) content ofthe still bottoms are reported on a dry basis using the method ofExample 1 to determine total dry solids. Nitrogen, phosphorus andpotassium content are determined by digestion using a sulfuric acid andhydrogen peroxide method followed by inductively coupled plasma atomicemission spectroscopy (ICP-AES) to determine N, P and K content (Thomaset al., 1967, Agronomy Journal, 59:240-243, which is incorporated hereinby reference). Sulfur is determined using HNO₃ and HClO₄ digestionfollowed by ICP-AES to determine S content (Blanchar et al., 1965, SoilScience of America Journal 29:71-72, which is incorporated herein byreference).

According to preferred embodiments, the inorganic component of the soilconditioning composition comprises at least nitrogen and sulfur. Theorganic component preferably comprises at least soluble lignin.

By the term “process chemical”, it is meant a chemical added at anystage during the production of the fermentation product from thelignocellulosic feedstock and/or subsequent steps to concentrate thefermentation product. This includes any chemical added during or beforethe production of sugar, fermentation and/or concentration of thefermentation product that results in the production of inorganic salt.Without being limiting, the process chemical may be used to adjust thepH of a process stream, provide nutrients for a biological process, suchas fermentation, or decontaminate a process stream.

Process chemicals added to the feedstock or process streams may includeacid and alkali. For example, acid or alkali may be used to pretreat orhydrolyze the lignocellulosic feedstock and/or may be added to a processstream to adjust its pH prior to a biological treatment such asenzymatic hydrolysis of cellulose and/or fermentation to a valueamenable to the enzyme and/or microorganism used in the fermentation.The acid or alkali process chemical may also be added to providenutrients to a microorganism used for fermentation and/or prevent thegrowth of unwanted microorganisms. The acid may be selected, forexample, from sulfuric acid and phosphoric acid and the alkali may beselected from ammonia, ammonium hydroxide, potassium hydroxide and lime.In further embodiments, the acid is selected from sulfuric acid andphosphoric acid and the alkali is selected from ammonia, ammoniumhydroxide and potassium hydroxide. The reaction of the acid and alkaliproduces inorganic salts, often significant amounts. Examples ofinorganic salts arising from the neutralization of the process chemicalsthat may be present in the still bottoms include ammonium sulfate,potassium sulfate, calcium sulfate, ammonium phosphate, potassiumphosphate and combinations thereof. In one embodiment, the inorganicsalts include ammonium sulfate, ammonium phosphate, potassium sulfate,potassium phosphate, or a combination thereof. In a further embodiment,the inorganic salts comprise ammonium sulfate or potassium sulfate. Inyet further embodiments, the inorganic salts comprise at least ammoniumsulfate.

Inorganic salts present in the soil conditioning composition may alsoarise from the feedstock itself. Without being limiting, lignocellulosicfeedstock often has a pH of between 6 and 10 due to the presence of thealkali minerals, such as potassium, sodium and calcium salts. Suchalkali minerals may include potassium carbonate, sodium carbonate andcalcium carbonate. Magnesium carbonate may be present as well dependingon the feedstock.

As discussed, the soil conditioning composition may comprise sulfur,which arises from the use of sulfur-containing process chemicals, suchas sulfuric acid in the production process. Sulfur in the still bottomsmay exist in the form of sulfate and/or bisulfate salts. This mayinclude sulfate and/or bisulfate salts of ammonium, potassium, sodium,calcium, magnesium or combinations thereof. According to one embodimentof the invention, the sulfur-containing salts present in the stillbottoms include, without limitation, potassium sulfate, potassiumbisulfate, sodium sulfate, sodium bisulfate, calcium sulfate, magnesiumsulfate, ammonium sulfate and combinations thereof. Preferably, thesulfur-containing salts include at least ammonium sulfate, potassiumsulfate or calcium sulfate. In another example of the invention, thesulfur-containing salt includes ammonium sulfate or calcium sulfate. Ina further embodiment, the sulfur-containing salt includes ammoniumsulfate. These salts are produced by reaction of sulfuric acid withsalts present in the incoming feedstock, such as during pretreatment,and/or reaction of sulfuric acid with alkali that is added as a processchemical, as described above, and/or during sulfuric acid additionduring a step of reducing the pH of a stream during fermentation to killunwanted microorganisms.

According to certain embodiments of the invention, the soil conditioningcomposition has a sulfur content of between about 1.0 and about 15 wt %,between about 1.0 and about 12 wt %, between about 1.5 and about 12 wt %or between about 2.0 and about 8 wt % as measured on a dry basis. In yetfurther embodiments, the still bottoms has a sulfur content of betweenabout 0.5 and about 15 wt %, between about 0.5 and about 12 wt % orbetween about 0.5 and about 8 wt %. The sulfur content may includeranges having numerical limits of about 0.5, 1.0, 1.5, 2.0, 3.0, 4.0,5.0, 6.0, 7.0, 8.0, 9.0, 10, 11, 12, 13, 14 or 15 wt % as measured on adry basis.

The soil conditioning composition may also comprise nitrogen, whicharises, at least in part, from the addition of nitrogen-containingprocess chemicals, such as ammonia or ammonium hydroxide. Nitrogen mayalso arise from protein present in the feedstock. Thenitrogen-containing process chemical may be added during pretreatment,after pretreatment to adjust the pH of a stream prior to biologicaltreatment, or to provide nutrients during fermentation. Nitrogen in thestill bottoms may exist in the form of ammonium salts. This may includeammonium salts of sulfate and/or chloride. According to one embodimentof the invention, the nitrogen-containing salts present in the stillbottoms include, without limitation, at least ammonium sulfate.

According to certain embodiments, the soil conditioning composition hasa nitrogen content of between about 2.0 and about 12 wt %, between about2.0 and about 10 wt %, or between about 2.0 and about 8 wt % on a drybasis. In further embodiments, the soil conditioning composition has anitrogen content of between about 1.0 and about 15 wt %, between about1.0 and about 12 wt %, between about 1.0 and about 10 wt % or betweenabout 1.0 and about 8 wt % on a dry basis. The nitrogen content mayinclude ranges having numerical limits of about 0.5, 1.0, 1.5, 2.0, 3.0,4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10, 11, 12, 13, 14 or 15 wt % as measuredon a dry basis.

Other nutrients that may be present in the soil conditioning compositioninclude chloride, iron, magnesium, boron, or a combination thereof.According to certain embodiments of the invention, the soil conditioningcomposition comprises chloride. The chloride content in the soilconditioning composition may be between about 0.1 and 2.0 wt % on a drybasis. The soil conditioning composition may be applied to soils thatare deficient in chloride.

According to some examples of the invention, the still bottoms in thesoil conditioning composition contains minimal phosphorus. The amount ofphosphorus present generally will depend on the feedstock used in themethod and from where it is sourced. Without being limiting, the soilconditioning composition may contain less than 2 wt % phosphorus, morepreferably, less than 1 wt % phosphorus on a dry basis, as measuredbased on the still bottoms component of the composition. Low levels orthe absence of phosphorus are advantageous for applications in which thestill bottoms are blended with manure. Manure often contains high levelsof phosphorus and thus blending the still bottoms with manure reduces oreliminates over-applying this nutrient to the soil, while at the sametime increases the concentration of desirable nutrients, such asnitrogen and sulfur. Thus, the soil conditioning composition of theinvention blended with manure, has a more balanced nutrient profile thanmanure alone.

The organics in the soil conditioning composition may comprise, withoutlimitation, insoluble and/or soluble lignin, lignin derived compounds,residual carbohydrates, non-fermented sugars, polyols, fermentationsolids or a combination thereof. Preferably, the organic componentcomprises at least soluble lignin. The organic component may includesoluble and insoluble components. According to some embodiments of theinvention, the organics do not include insoluble lignin.

The soluble lignin content of the soil conditioning composition may bebetween about 5.0 and about 50 wt %, or between about 10 and about 20 wt% on a dry basis, as measured based on the still bottoms component ofthe composition.

Insoluble lignin and unconverted solids may also be present if thesecomponents are not removed in upstream stages of the process.Preferably, insoluble lignin is removed in upstream stages prior torecovery of the still bottoms. According to some embodiments of theinvention, insoluble lignin is removed from a process stream prior torecovery of the still bottoms and then mixed with the still bottoms.

Advantageously, the soil conditioning composition of the presentinvention does not contain significant quantities of carbohydrate.Carbohydrate is a valuable substrate that is used to produce fermentablesugar. Typically, the soil conditioning composition will comprise lessthan 2 wt % or 1 wt % cellulose or hemicellulose, which is derived fromthe lignocellulosic feedstock fed to the production process. Celluloseand hemicellulose are measured on a dry basis on the still bottomscomponent of the composition.

The soil conditioning composition may contain between about 10 and about88 wt % moisture, or between about 25 and about 45 wt % moisture.

As noted, in addition to still bottoms, other components may be includedin the soil conditioning composition. These components include aresidue, byproduct or waste from the processing of plant biomass. Suchresidue, byproduct or waste may originate from the above-describedproduction process itself that uses a lignocellulosic feedstock as astarting material to make a fermentation product. An example of such acomponent is lignin. In further embodiments, the still bottoms may becombined with a residue, byproduct or waste from the processing of asugar or starch crop to make a food or non-food product.

Thus, according to certain embodiments, the present invention provides amethod comprising: (i) providing still bottoms from a process thatproduces a fermentation product from a lignocellulosic feedstock; and(ii) combining the still bottoms with a residue, byproduct, or wastefrom the processing of a plant biomass to produce a soil conditioningcomposition. The plant biomass may be a sugar crop, a starch crop or alignocellulosic feedstock. The residue, byproduct or waste may includesugar cane bagasse, vinasse, corn fiber, distillers grain, lignin or acombination thereof. In one embodiment, the plant biomass is a sugarcrop or a starch crop. The sugar crop or starch crop may include corn,wheat, barley, rye, sorghum, rice, potato, cassava, sugar beet, sugarcane, or a combination thereof. In a further embodiment of theinvention, the residue, byproduct or waste is sugar cane bagasse,vinasse, or a combination thereof, from the processing of sugar cane.

Use of the Composition as a Soil Conditioner

The soil conditioning composition or still bottoms is provided for usein a land application. This includes transporting or arranging for thetransportation of the soil conditioning composition or still bottoms toa farming operation. A suitable transportation method is trucking. Bythe term “land application”, it is meant applying the soil conditioningcomposition or still bottoms using any known or later-developedtechnique for adding or incorporating the soil conditioning compositionor still bottoms to a field, including, but not limited to, irrigationequipment or liquid manure injection systems. The field to which thesoil conditioning composition or still bottoms is applied may or may notbe tilled or worked in any way prior to the land application.

The soil conditioning composition or still bottoms may be stored at afarming operation prior to use. Storage is carried out in any suitablecontainment means, such as tanks, basins or lagoons. The soilconditioning composition or still bottoms can be agitated or there maybe no agitation during storage. Ventilation and/or odour control methodsmay be utilized if required during storage. As would be appreciated bythose of skill in the art, storage requirements would typically be basedon agricultural growing seasons and the location of the farmingoperation. Agitation could be required before application and after astorage period to ensure a somewhat homogenous product.

According to some embodiments of the invention, the soil conditioningcomposition or still bottoms that is applied to the soil comprisesmanure. The manure may be added to the soil conditioning composition orstill bottoms during storage.

The soil conditioning composition or still bottoms may contain betweenabout 10 and about 88 wt % moisture. Preferably, the soil conditioningcomposition or still bottoms has a solids consistency that enables it tobe applied to land using conventional equipment in a farming operation.By this it is meant that the soil conditioning composition or stillbottoms has sufficient liquid content that it is capable of being pumpedor otherwise applied to a field by farm equipment such as irrigationequipment or by farming equipment that are conventionally used to applymanure or liquid fertilizer to fields at a farming operation, such as byspreading, spraying or injecting. Preferably, the soil conditioningcomposition or still bottoms is a liquid composition that is capable offlowing or being pumped. At elevated solids consistencies it iscontemplated that distributor systems could be utilized as is the casewith bedded manure or thicker slurries.

Where the material does not flow readily, equipment used for solidmanure applications is contemplated for land application. Alternatively,liquid, in any form, can be added back to the soil conditioningcomposition or still bottoms so it can be handled as a liquid slurry.Land application of the soil conditioning composition or still bottomsby irrigation equipment or using other farm equipment is particularlyadvantageous in that it allows a farming operation to use conventionalequipment and methods that are currently practiced in the industry.Thus, a farming operation need not change their current techniques forapplying organic amendments to a field (such as manure) when applyingthe soil conditioning composition or still bottoms of the presentinvention. Accordingly, this saves on capital and operating costs thatwould otherwise be required.

The application rate of the soil conditioning composition or stillbottoms to soil may depend on recommended application rates, which inturn are based on soil condition and nutrient requirements. Soilcondition may be determined by carrying out a soil analysis test. It isparticularly beneficial to apply the soil conditioning composition orstill bottoms of the invention to sandy soils, or soils that are proneto water and wind erosion, thereby introducing organic content to thesoil, along with nutrients.

EXAMPLES Example 1: Determination of the Total Solids Concentration inLignocellulosic Still Bottoms

The determination of the total solids (TS) content of still bottoms iscarried out as follows.

A still bottoms sample is transferred to a pre-weighed aluminum tin andthe mass of the tin and sample is determined gravimetrically. The sampleis then oven dried at 105° C. to constant mass (typically 24 hours). Thecombined mass of the dried solids and tin are measured gravimetrically.The total solids content is calculated by dividing the dried sample massby the initial sample mass and expressed as a percentage.

Example 2: Determination of the Organic Components in LignocellulosicStill Bottoms

The organic components in a still bottoms sample are determined byquantifying identified and unidentified components. The percentageorganic component is measured by weight on a dry basis using the methodset out in Example 1 to determine the total dry solids content. Sugars,including glucose, xylose and arabinose are measured by HPLC using aCarboPac™ PA1 column (4×250 mm) consisting of a 10 μm diameterpolystyrene/divinylbenzene substrate agglomerated with 580 nm MicroBeadquaternary ammonium functionalized latex (2% cross linkage) and a 100μeq/column anion exchange capacity (4×250 mm).

Organic acids such as acetic acid, lactic acid, glucuronic acid andgalacturonic acid are measured using high performance liquidchromatography (HPLC) on a Dionex system, with an IonPac®AS11-HC column(4×250 mm) that consists of a 9 μm diameter ethylvinylbenzene polymercross linked with 55% divinylbenzene polymer agglomerated with a 70 nmalkanol quaternary ammonium latex (6% latex cross linkage) and acapacity of 290 μeq/column (4×250 mm).

The lignin content of the sample was measured via ultraviolet absorbance(UV) at 205 nm using absorption coefficients to estimate theconcentration.

The protein concentration was determined using the Kjeldahl nitrogenmeasurement, using a factor of 6.25 to convert from the measurednitrogen value to the protein content. The Kjeldahl nitrogen measurementis carried out as described in Standard Methods for the Examination ofWater and Wastewater, 21^(st) Edition, 2005, ppg. 4-131-4132, ref#4500-N_(org) B, BUCHI Instructions Distillation Unit K-355, which isincorporated herein by reference.

There is also a fraction of the total organic content that is of unknownidentity. The total mass of this fraction was determined from a totalorganic carbon (TOC) measurement. The theoretical TOC content of theknown components was subtracted from the total TOC to estimate theunknown organic carbon content. The TOC is measured using a SieversInnovOx (Innovative Oxidation) Laboratory and On-Line Total OrganicCarbon (TOC) Analyzer based on Supercritical Water Oxidation (SCWO). Thetechnique brings water to a supercritical state by heating a watersample inside a sealed reactor module to 375° C. and raising thepressure to 3200 psi. Under these conditions, water is neither a gas nora liquid, but exhibits beneficial properties of both. The TOCmeasurement is carried out as described in Standard Methods for theExamination of Water and Wastewater, 21^(st) Edition, 2005, ppg.5-19-5-22, ref #5310 or as set forth in U.S. Pat. No. 8,114,676, bothwhich are incorporated herein by reference.

Example 3: Determination of the Inorganic Components in a Still BottomsComposition from Processing a Lignocellulosic Feedstock

The determination of the inorganic components in the still bottoms ofthe invention is carried out as follows. The percentage inorganiccomponent is measured by weight on a dry basis using the method set outin Example 1 to determine the total dry solids content.

Anions such as chloride, phosphate and sulfate are measured using highperformance liquid chromatography (HPLC) on a Dionex system, with anIonPac®AS11-HC column (4×250 mm) that consists of a 9 μm diameterethylvinylbenzene polymer cross linked with 55% divinylbenzene polymeragglomerated with a 70 nm alkanol quaternary ammonium latex (6% latexcross linkage) and a capacity of 290 μeq/column (4×250 mm).

Cations such as sodium, potassium, magnesium and calcium are measuredusing a Dionex system, with an IonPac®CS16 column (5×250 mm) thatconsists of a 5.5 μm diameter ethylvinylbenzene polymer cross linkedwith 55% macroporous divinylbenzene polymer (100 Å) agglomerated withcarboxylic acid functional groups and a capacity of 8400 μeq/column(5×250 mm).

Example 4: Nutrient Profile of a Still Bottoms Stream

This example shows the nutrient profile of a still bottoms streamobtained from a process that produces a fermentation product from alignocellulosic feedstock. FIG. 1 shows the nitrogen, phosphorus,potassium and sulfur content of a still bottoms stream, as well as thesoluble lignin and moisture content.

The values in the figure are based on still bottoms in which wheat strawwas pretreated with sulfuric acid under conditions described in U.S.Pat. No. 7,754,457, which is incorporated herein by reference. Afterpretreatment, the pretreated feedstock slurry is pH adjusted to a valuebetween 4 and 6 with ammonia to produce a pretreated feedstock slurrycomprising ammonium sulfate, and the cellulose in the slurry ishydrolyzed with cellulase enzymes to a produce a hydrolyzed slurrycomprising glucose. After enzymatic hydrolysis, lignin and otherinsoluble components are removed from the hydrolyzed slurry by a filterpress. The filtered stream is sent to a fermentation that is conductedwith a Saccharomyces cerevisiae strain capable of fermenting glucose andxylose to ethanol. Fermentation results in a beer that is sent todistillation and molecular sieves for concentration of ethanol. Thestill bottoms remaining after distillation is evaporated in anevaporator to a moisture content of 53.7 wt %. Ammonium sulfate from theneutralization of the pretreated feedstock is carried through to thestill bottoms.

As can be seen in FIG. 1, the still bottoms comprise nitrogen, potassiumand sulfur at levels that can increase the nutrient content of soil. Asillustrated in FIG. 1, there is no phosphorus present, although thecontent can vary depending on the batch. This is particularlyadvantageous, since manure often contains high levels of phosphorus andthus blending the still bottoms with manure reduces or eliminatesover-applying this nutrient to the soil, while at the same timeincreasing the concentration of desirable nutrients, such as nitrogenand sulfur. Therefore, blending the still bottoms with manure yields asoil conditioning composition that has a more balanced nutrient profilethan manure alone.

In addition, the moisture content of the still bottoms is high enoughthat the still bottoms stream can be pumped, which allows it to beapplied to the land using current practices.

Example 5: Test Results of Land Application of Still Bottoms

This example demonstrates that land application of the still bottomsprovides nutrients to crops at similar levels provided by a chemicalfertilizer. The results presented below show that leaf tissue sulfur,phosphorus, potassium and nitrogen in crops treated with still bottomswere present at levels similar to plants treated with chemicalfertilizer. The health and condition of the crop was also determined bymeasuring chlorophyll content in plant leaves and the data collectedshow that chlorophyll content was similar in studies using still bottomsand chemical fertilizer. In addition, test results show that the stillbottoms did not have a negative impact on plant population relative tothe application of chemical fertilizer. Together, these results showthat the still bottoms derived from lignocellulosic feedstock canprovide benefits to crops that are similar to those achieved withchemical fertilizer.

In this example, still bottoms samples resulting from the productionprocess described in Example 4 were used to treat corn crops of thevariety Dekalb 6323. The batch used in the land application study wasanalyzed for nutrient content and the results of this analysis arepresented in Table 1 below. Weight percentages are measured on a drybasis.

TABLE 1 Nutrient analysis of still bottoms Nutrient Concentration TotalN (wt %) 4.8 S (wt %) 1.7 K (wt %) 0.5 Mg (wt %) 0.5 P (wt %) 0.3 Ca (wt%) 0.05 Cu (ppm) 4 Fe (ppm) 13 Mn (ppm) 72 Zn (ppm) 1.0

Chemical fertilizer and still bottoms were applied at 5 rates based on N(0, 50, 100, 150, and 200 lbs N/acre). Sulfur fertilizer was alsoapplied at equivalent rates supplied by the still bottoms stream.Individual plots in the field were 15×50 ft. Before planting, a chiselwas used to form ridges in the soil and liquid still bottoms wasmanually applied for control of amount and uniformity. A disk operationfollowed to level the soil. The experimental design consisted of arandomized complete block with 4 replications.

The nitrogen application rate was adjusted based on a sample analysisconducted at the time that the still bottoms were applied to the crop.The nitrogen application rate (in both lbs/acre and kg/ha) at the 5rates tested for the chemical fertilizer and still bottoms is providedin Table 2 below.

TABLE 2 Final nitrogen application rate for chemical fertilizer andstill bottoms Fertilizer Still bottoms Fertilizer Still bottomsTreatment lbs/acre kg/ha 1 50 41 56 46 2 100 83 112 93 3 150 124 168 1394 200 166 224 185

At the six-leaf (V6) growth stage, the aboveground plant parts wereharvested and weighed for the fresh weight. Plant materials were washedto remove soil particles and dried in a forced air oven at 60° C. for 4days (or until constant weight is achieved) and weighed (to obtain dryweight) for biomass calculation. Once dried, plants were ground with aWiley grinder and stored in appropriate air-tight vials. Sub-samples ofground plant materials were digested using a sulfuric acid and hydrogenperoxide method (Thomas et al., 1967, Agronomy Journal, 59:240-243,which is incorporated herein by reference) and analysed with inductivelycoupled plasma atomic emission spectroscopy (ICP-AES) for N, P and K.Another sub-sample of ground plant material were digested using HNO₃ andHClO₄ (Blanchar et al., 1965, Soil Science of America Journal 29:71-72,which is incorporated herein by reference) and analysed for S byICP-AES.

The results of the nutrient analysis on the plant material are presentedin FIGS. 2A-D. FIG. 2A shows the leaf tissue content of sulfur for stillbottoms and fertilizer at the given nitrogen application rates measuredin lbs/acre. At each application rate, the leaf tissue sulfur levelswere comparable for still bottoms and chemical fertilizer. FIGS. 2B, 2Cand 2D show the leaf tissue content of phosphorus, potassium andnitrogen, respectively, for still bottoms and fertilizer at the givennitrogen application rates measured in lbs/acre. For each plant nutrientmeasured, the leaf tissue content of the elements was similar for bothstill bottoms and chemical fertilizer. In FIG. 2D, the leaf tissuenitrogen content was slightly less for the still bottoms samples thanthe fertilizer, but this is likely due to the lower nitrogen applicationrate of the still bottoms stream (see Table 2 above).

Chlorophyll in plant tissue was also measured after application of stillbottoms and the chemical fertilizer. The results are depicted in FIG. 3,which shows the chlorophyll meter reading at the tasseling stage of thecorn at each nitrogen application rate tested. Chlorophyll contentprovides an indication of the health and condition of a plant. As can beseen in FIG. 3, the chlorophyll readings were similar for treatment withstill bottoms and chemical fertilizer.

The impact of still bottoms and fertilizer application on the populationof the corn crop was also analyzed. An analysis of variance betweengroups (ANOVA analysis) indicated that there was no statisticallysignificant difference of plant population after land application ofstill bottoms or the fertilizer (results not shown). Results presentedin FIG. 4 show plants/hectare at each nitrogen application rate forstill bottoms and chemical fertilizer application. The plants/hectarewere similar for still bottoms and chemical fertilizer application ateach application rate tested. These results show that still bottoms werenot toxic to the plants.

The invention claimed is:
 1. A process for producing a fuel fromlignocellulosic feedstock, said fuel comprising ethanol, said processcomprising: (i) treating the lignocellulosic feedstock to produce sugar;(ii) fermenting the sugar to produce a fermented mixture comprising theethanol; (iii) recovering the ethanol from the fermented mixture in oneor more stages to produce a concentrated ethanol and still bottoms; (iv)recovering the still bottoms, said still bottoms comprising an organiccomponent and an inorganic component; and (v) applying the still bottomscomprising the organic component and the inorganic component to land asa soil conditioner, wherein applying the still bottoms to the landreturns at least one member selected from the group consisting oforganic matter and nutrients back to the land.
 2. The process of claim1, wherein the still bottoms applied to land as a soil conditionercomprises 40-80 wt % organic components and 20-60 wt % inorganiccomponents on a dry basis.
 3. The process of claim 1, wherein theinorganic components originate from the lignocellulosic feedstock,process chemicals added during said process, or a combination thereof.4. The process of claim 1, wherein the inorganic components originatefrom both the lignocellulosic feedstock and process chemicals addedduring said process.
 5. The process of claim 1, wherein the step ofrecovering the still bottoms comprises concentrating the still bottoms.6. The process of claim 1, wherein the organic component comprisesdissolved lignin, insoluble lignin or a combination thereof.
 7. Theprocess of claim 1, wherein the still bottoms has a phosphorus contentof less than 2 wt % on a dry basis.
 8. The process of claim 1, whereinthe still bottoms has a solids content that allows it to be pumpedthrough farming equipment.
 9. The process of claim 1, wherein the stepof recovering the still bottoms comprises separating solids from thestill bottoms, thereby producing a residue stream composed of separatedsolids and a liquid component and wherein the separated solids and theliquid component are each provided for use in soil conditioning.
 10. Theprocess of claim 1, wherein the step of treating comprises pretreatingthe lignocellulosic feedstock with acid or alkali to produce acomposition comprising cellulose and hydrolyzing at least a portion ofthe cellulose to glucose with enzymes.
 11. The process of claim 1,comprising adding insoluble lignin to the still bottoms prior to step(v).
 12. The process of claim 1, wherein said ethanol is characterizedby a sustainability improvement provided by using less chemicalfertilizer to restore nutrient levels to the land, said sustainabilityimprovement being relative to a process wherein nutrients are returnedback to the land by chemical fertilizers.
 13. The process of claim 1,wherein said ethanol is characterized by a greenhouse gas emissionsreduction associated with using less chemical fertilizer to restorenutrient levels to the land.
 14. The process of claim 1, wherein saidethanol is characterized by a greenhouse gas emissions reductionassociated with applying the still bottoms to the land.
 15. A processfor producing a fuel from lignocellulosic feedstock, said fuelcomprising ethanol, said process comprising: (i) treating thelignocellulosic feedstock to produce sugar; (ii) fermenting the sugar toproduce a fermented mixture comprising the ethanol; (iii) recovering theethanol from the fermented mixture in one or more stages to produceconcentrated ethanol and still bottoms; (iv) recovering the stillbottoms, said recovered still bottoms comprising 40-80 wt % organiccomponent and 20-60 wt % inorganic component, said organic componentcomprising at least soluble lignin, said inorganic component comprisingat least nitrogen and sulfur; and (v) applying the still bottomscomprising the organic component and the inorganic component to land asa soil conditioner, wherein the life cycle greenhouse gas emissions ofthe ethanol is reduced relative to life cycle greenhouse gas emissionsof ethanol produced by an otherwise identical fuel production processthat does not apply the still bottoms to land as a soil conditioner, andwherein said reduction is at least in part a result of step (v).
 16. Theprocess of claim 15, wherein the organic component further comprisessugar, insoluble lignin, or a combination thereof.
 17. The process ofclaim 15, wherein the inorganic component further comprises potassium,chloride, magnesium, calcium or a combination thereof.
 18. The processof claim 15, wherein the phosphorus content is less than about 2 wt % ona dry basis.
 19. The process of claim 15, wherein the water content isbetween about 10 and about 90 wt %.
 20. The process of claim 15, whereinthe water content is between about 20 and about 50 wt %.
 21. A processfor producing a fuel from lignocellulosic feedstock, said fuelcomprising ethanol, said process comprising: (i) treating thelignocellulosic feedstock to produce sugar; (ii) fermenting the sugar toproduce a fermented mixture comprising ethanol; (iii) recovering theethanol from the fermented mixture in one or more stages to producerecovered ethanol and still bottoms; (iv) recovering the still bottoms,said recovered still bottoms comprising 40-80 wt % organic component and20-60 wt % inorganic component, said organic component comprising atleast soluble lignin, said inorganic component comprising at leastnitrogen and sulfur; and (v) conditioning soil by applying the stillbottoms comprising the organic component and the inorganic component toland, wherein the life cycle greenhouse gas emissions of the ethanol isreduced relative to life cycle greenhouse gas emissions of ethanolproduced by an otherwise identical fuel production process that includesdisposing of the still bottoms by incineration rather than applying thestill bottoms to land.